Report messages instead of just printing.

pkg/front_end/lib/src/fasta/testing/validating_instrumentation.dart

 // Copyright (c) 2017, the Dart project authors. Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE.md file.
 import 'dart:async';
 import 'dart:convert';
 import 'dart:io';
 
 import 'package:front_end/src/base/instrumentation.dart';
+import 'package:front_end/src/fasta/compiler_context.dart' show CompilerContext;
 import 'package:front_end/src/fasta/messages.dart';
 import 'package:front_end/src/fasta/scanner.dart';
 import 'package:front_end/src/fasta/scanner/io.dart';
+import 'package:front_end/src/fasta/severity.dart' show Severity;
 import 'package:front_end/src/scanner/token.dart' as analyzer;
 
 /// Implementation of [Instrumentation] which checks property/value pairs
 /// against expectations encoded in source files using "/*@...*/" comments.
 class ValidatingInstrumentation implements Instrumentation {
   static final _ESCAPE_SEQUENCE = new RegExp(r'\\(.)');
 
   /// Map from feature names to the property names they are short for.
   static const _FEATURES = const {
     'inference': const [
@@ skipping 171 matching lines @@
   String _escape(String s) {
     s = s.replaceAll(r'\', r'\\');
     if (s.endsWith('/')) {
       s = '$s ';
     }
     return s.replaceAll('/*', r'/\*').replaceAll('*/', r'*\/');
   }
 
   String _formatProblem(
       Uri uri, int offset, String desc, StackTrace stackTrace) {
-    return deprecated_format(
-        uri, offset, '$desc${stackTrace == null ? '' : '\n$stackTrace'}');
+    return CompilerContext.current.format(
+        templateUnspecified
+            .withArguments('$desc${stackTrace == null ? '' : '\n$stackTrace'}')
+            .withLocation(uri, offset),
+        Severity.internalProblem);
   }
 
   String _makeExpectationComment(String property, InstrumentationValue value) {
     return '/*@$property=${_escape(value.toString())}*/';
   }
 
   void _problem(Uri uri, int offset, String desc, _Fix fix) {
     _problems.add(_formatProblem(uri, offset, desc, null));
     _fixes.putIfAbsent(uri, () => []).add(fix);
   }
@@ skipping 26 matching lines @@
       this.property, this.value, this.commentOffset, this.commentLength);
 }
 
 class _Fix {
   final int offset;
   final int length;
   final String replacement;
 
   _Fix(this.offset, this.length, this.replacement);
 }